Voltage control device

Abstract

A device for controlling a first voltage with a second voltage includes a first terminal of application of the second voltage and a second terminal for supplying the first voltage. A comparator has a first input terminal connected to the first terminal and has a second input terminal receiving information representative of the first voltage. At least one first current source of programmable intensity is connected to the second input terminal of the comparator.

What is claimed is: 
     
       1. A device for controlling a first voltage with a second voltage, the device comprising:
 a first terminal configured to receive the second voltage; 
 a second terminal configured to supply the first voltage; 
 a comparator having a first input terminal connected to the first terminal and a second input terminal configured to receive information representative of the first voltage; 
 a current source of programmable intensity connected to the second input terminal; 
 a variable resistor coupled between the second input terminal and a first supply terminal; and 
 a resistor coupled between the second terminal and the second input terminal, wherein the device is configured to cancel a voltage offset at the second terminal by adjusting a compensation current supplied by the current source and without changing a resistance of the variable resistor, wherein the first voltage is substantially equal to the second voltage times a gain plus the voltage offset. 
 
     
     
       2. The device of  claim 1 , wherein the current source is configured to generate a current that is proportional to a ratio of the second voltage to a resistance. 
     
     
       3. The device of  claim 1 , wherein the current source is coupled between the first supply terminal or a second supply terminal and the second input terminal. 
     
     
       4. The device of  claim 3 , wherein the first supply terminal is configured to receive a power supply voltage. 
     
     
       5. The device of  claim 4 , wherein the power supply voltage is ground. 
     
     
       6. The device of  claim 1 , wherein the current source comprises:
 a first branch comprising a reference current source and a first transistor, the first transistor having a current path that is coupled in series with the reference current source; and 
 a second branch comprising a programmable switch and a second transistor, the second transistor having a current path that is coupled in series with the programmable switch, wherein the current path of the second transistor is coupled to the second input terminal, and wherein a control terminal of the second transistor is coupled to a control terminal of the first transistor. 
 
     
     
       7. The device of  claim 6 , further comprising a second current source of programmable intensity coupled between a second supply terminal and the second input terminal, wherein the current source is coupled between the first supply terminal and the second input terminal. 
     
     
       8. The device of  claim 7 , wherein the second current source comprises:
 a first branch comprising a second reference current source and a third transistor, the third transistor having a current path that is coupled in series with the second reference current source; and 
 a second branch comprising a second programmable switch and a fourth transistor, the fourth transistor having a current path that is coupled in series with the second programmable switch, wherein the current path of the fourth transistor is coupled to the second input terminal, and wherein a control terminal of the fourth transistor is coupled to a control terminal of the third transistor. 
 
     
     
       9. The device of  claim 1 , wherein the current source comprises a programmable voltage source and a resistor coupled in series between a ground terminal and the second terminal of the comparator. 
     
     
       10. A circuit comprising:
 a comparator having a first input, a second input, and an output configured to produce an output voltage; 
 a resistor coupled between the output of the comparator and the second input of the comparator; 
 a reference voltage generator coupled to the first input of the comparator and configured to generate a reference voltage; 
 a programmable current source coupled between a first reference voltage terminal and the second input of the comparator; and 
 a variable resistor coupled between the second input of the comparator and a first supply terminal, wherein the circuit is configured to cancel a voltage offset at the output of the comparator by adjusting a compensation current supplied by the programmable current source and without changing a resistance of the variable resistor, wherein the output voltage is substantially equal to the reference voltage times a gain plus the voltage offset. 
 
     
     
       11. The circuit of  claim 10 , further comprising a second programmable current source coupled between a second reference voltage terminal and the second input of the comparator. 
     
     
       12. The circuit of  claim 10 , wherein the programmable current source comprises:
 a first branch comprising a diode-coupled transistor in series with a reference current source, the first branch coupled between the first reference voltage terminal and a second reference voltage terminal; and 
 a second branch comprising a programmable switch in series with a second transistor, the second branch coupled between the first reference voltage terminal and the second input of the comparator. 
 
     
     
       13. The circuit of  claim 12 , wherein the programmable current source further comprises a third branch comprising a second programmable switch in series with a third transistor, the second branch coupled between the first reference voltage terminal and the second input of the comparator. 
     
     
       14. A circuit comprising:
 a comparator having a first input, a second input, and an output configured to produce an output voltage; 
 a resistor coupled between the output of the comparator and the second input of the comparator; 
 a reference voltage generator coupled to the first input of the comparator and configured to generate a reference voltage; 
 a first programmable current source coupled between a first reference voltage terminal and the second input of the comparator; 
 a second programmable current source coupled between a second reference voltage terminal and the second input of the comparator; and 
 a variable resistor coupled between the second input of the comparator and the second reference voltage terminal, wherein the circuit is configured to cancel a voltage offset at the output of the comparator by adjusting a compensation current supplied by the first or second programmable current sources and without changing a resistance of the variable resistor, wherein the output voltage is substantially equal to the reference voltage times a gain plus the voltage offset. 
 
     
     
       15. The circuit of  claim 14 , wherein the first programmable current source comprises:
 a first branch comprising a diode-coupled transistor in series with a reference current source, the first branch coupled between the first reference voltage terminal and the second reference voltage terminal; and 
 a second branch comprising a programmable switch in series with a second transistor, the second branch coupled between the first reference voltage terminal and the second input of the comparator, the second transistor having a gate coupled to a gate of the diode-coupled transistor. 
 
     
     
       16. The circuit of  claim 15 , wherein the first programmable current source further comprises a third branch comprising a second programmable switch in series with a third transistor, the second branch coupled between the first reference voltage terminal and the second input of the comparator, the third transistor having a gate coupled to the gate of the second transistor. 
     
     
       17. The circuit of  claim 15 , wherein the second programmable current source comprises:
 a first branch comprising a second diode-coupled transistor in series with a second reference current source, the first branch coupled between the first reference voltage terminal and the second reference voltage terminal; and 
 a second branch comprising a second programmable switch in series with a third transistor, the second branch coupled between the second reference voltage terminal and the second input of the comparator, the third transistor having a gate coupled to a gate of the second diode-coupled transistor. 
 
     
     
       18. The circuit of  claim 14 , wherein the first reference voltage terminal is a VDD terminal and the second reference voltage terminal is a ground terminal. 
     
     
       19. The circuit of  claim 10 , wherein the resistor is directly connected between the output of the comparator and the second input of the comparator. 
     
     
       20. The circuit of  claim 14 , wherein the resistor is directly connected between the output of the comparator and the second input of the comparator. 
     
     
       21. The device of  claim 1 , wherein an output of the comparator is connected to the second input terminal via the resistor.